Chain guards needed or not on this robot

My specific question is do we need chain guards on the chain that drives our climber. Its a slow moving chain, and the large sprocket rotates in a range of about 270 degrees. Movement is triggered by a button on the remote (nothing autonomous).

My more general question: are there written rules about when chain guards are needed? I know the LRI’s will have final say in whether we do or do not need guards, but what are they basing that decision off of? Are they provided guidance from FIRST? Is is based on velocity of the chain? Location of it? I’m trying to have the knowledge necessary to be ready to go when we get to the competition. Thanks.

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We have never once guarded a chain or belt on a robot. shrug No one should be anywhere near them when they are running, and the number of pinch points and other safety issues on a 150 lb 17 fps piece of motorized metal really make chain guards safety theater, in my opinion.

If it’s enabled, stay the heck away.

Especially on your robot - the exposed chain is low speed. I wouldn’t be too nervous about it.


I can speak for FIM in my experience it is left up to the head inspector at each event. My team had very similar arms and while nothing in the rule book (to my knowledge it’s been a while and I mentor now) outlines chain guards we were told to put guards on or we could not compete.

I don’t think you’ll be stopped from competing in it’s current state (depends on the LRI), but I’d really recommend you put something there regardless. Especially where the chain starts/stops contacting the large sprocket. Because it’s facing outward, the risk of injury is high. I especially foresee an issue when removing it from the bars.

Yes, no one should be near that when it’s running, but kids grab the robot in weird places when carrying it, and if your team is anything like mine, marketing/operations kids who know very little about robots keep touching it when it’s on. Also if someone moves the arm manually, it could do some damage to fingers. Just because it’s low speed doesn’t mean it’s not dangerous, it just means it’s high torque.

It’s pretty easy to 3D model some little guards and 3d print them out.


It will be left up to the LRI at your event…

The guarding is a R203 sort of thing so it is completely up to the LRI. If I were to require guarding, that would be something I would require it on. At least something to protect nip points on the big gear. A poly disk maybe? While it is guarded by the field fencing in the field, what protection is on place on it in the pits? If I was inspecting your robot, I would at least show that to the LRI.

OSHA standards (which does not cover FRC robots) require full guarding on all nip points. IE chain engaging in the sprocket teeth. Speed does not matter.


That needs to be fixed - along with the timeouts. The answer to this stuff should never be “it depends”. But I don’t know how you could make a decent rule that isn’t overly restrictive.


Indeed. We’ve been forced to guard some chains and had other chains allowed to run unguarded. No rhyme or reason beyond the particular inspector we were assigned.

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Someone want to dig out the 2006 rules? That year required all sorts of chain guards, and heaven help you if a 3/4" dowel could get to the chain/sprocket.

They’ve backed way off since then.

These really are the points that I would look to guard if it’s possible, along with the smaller sprocket at the bottom of the chain run.

Can that arm move, even a little, when unpowered (Ie, can it move when lifting it off the bar, carrying off the field, steadying it while pushing your cart through the venue, etc)? With it being relatively high and on the outside of the robot, it seems to be in a location at/near where you might grab/hold on to it at various times, which could be disastrous if things move unexpectedly (and we’ve all see unexpected movement on robots!).


To those claiming this is “safety theater” - what happens if student A has their hand in the chain near one of those pinch points, while student B presses on the end of the arm over at the other end of the robot? This isn’t a contrived scenario.


Since as far as I know, I am the only ‘those’ that mentioned safety theater I guess I should respond. We’re going to have to agree to disagree. Playing the ‘what if’ game is a slippery slope that ends up in these robots not competing at all.

A list of things that are ‘dangerous’ is simply too long to create.
It would be too dangerous to move robots on carts without auto-locking brakes and bumpers.
Too dangerous to have anyone with 10 feet of field side because they might reach or tip over
Too dangerous to have field setup on the field while teams are moving their robots
Too dangerous to let them climb because of the mechanics of lifting them down…
Too dangerous to run robots on the practice fields at all
Too dangerous to run the robots tethered without guards between us and them

And so on.

I don’t want to see a return of chain guards.

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This seems like a slippery slope to me. Obviously, any safety practice can be inconvenient/counterproductive if taken to an extreme. Guarding the obvious pinch points on the OP’s robot does not seem to me to be an extreme.

Alternatively, the team could demonstrate that they’re able to lock the movement of the arm while working on it.

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How long an arm must be locked? How heavy? What if it’s tiny but spring loaded? Define arm.

I’m not disagreeing just for the sake of disagreeing. Once you go down the safety rule road you need to begin to define everything - and assume the risk of your rules if they are incomplete and someone who assumes they are safe gets hurt.
I think safety should be left to teams.

If the question comes to your mind then I would recommend some sort of chain guard. If for no other reason it says to the inspector. “we saw this as a potential issue and this is what we did” I think inspectors are more likely to worry about a missed issue in a robot than disagreements in a particular solution to that issue.

I’d almost always guard sprockets like this out in the open, especially anything that has that much torque. I’m biased though, I’ve been on the receiving end of a sprocket and bike chain while doing regular maintenance.

At the minimum, paint the sprocket a bright yellow (oh hey 330) or very clearly call out the pinch points.

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You’re really suggesting that there should be no safety rules at all?

No. I’m not.

I’m not seeing what else “leaving safety to teams” could entail. The argument you’ve given applies equally against any conceivable safety rule, no matter its costs or benefits.

There were several robots at a week 2 event that had an exposed sprocket and chain on their intake mechanism that lost the chains after taking a hit. While the OP’s chains and sprockets don’t look like they extend beyond their frame perimeter, they look rather vulnerable to damage from other robots. There are foul points and penalties assessed when an opponent robot intrudes in your frame perimeter, but none are assessed when a robot from the same alliance intrudes into your frame perimeter. Sometimes, it almost looks like robots on the same alliance are playing defense on each other as they jockey for position to execute a last minute climb.